Post-Mortem Study of Two 100 MW GSU Power Transformers

This paper presents a detailed post-mortem analysis of two identical 100 MW GSU power transformers, both exposed to the same operational load. The main objective of this study was to evaluate and compare key diagnostic parameters such as dissolved gas analysis (DGA), dielectric breakdown strength, moisture content, acidity levels, and loss factor. Additionally, it focused on understanding the effects of oil regeneration on oil quality and insulation health, exploring how this maintenance practice could impact the long-term reliability of high-power transformers. The comparative analysis of the key diagnostic parameters of both transformers concluded that they are a useful tool to discover different aging rates in similar transformers. Additionally, it was detected that the regenerated oil had significantly lower moisture and acidity levels than the untreated oil, supporting the benefits of oil regeneration in maintaining quality. It was also detected that regenerated oil had a lower loss factor, reflecting improved insulation quality and demonstrating that oil regeneration helps maintain fluid properties and reduce operational losses.